macvlan: add source mode

This patch adds a new mode of operation to macvlan, called "source".
It allows one to set a list of allowed mac address, which is used
to match against source mac address from received frames on underlying
interface.
This enables creating mac based VLAN associations, instead of standard
port or tag based. The feature is useful to deploy 802.1x mac based
behavior, where drivers of underlying interfaces doesn't allows that.

Configuration is done through the netlink interface using e.g.:
 ip link add link eth0 name macvlan0 type macvlan mode source
 ip link add link eth0 name macvlan1 type macvlan mode source
 ip link set link dev macvlan0 type macvlan macaddr add 00:11:11:11:11:11
 ip link set link dev macvlan0 type macvlan macaddr add 00:22:22:22:22:22
 ip link set link dev macvlan0 type macvlan macaddr add 00:33:33:33:33:33
 ip link set link dev macvlan1 type macvlan macaddr add 00:33:33:33:33:33
 ip link set link dev macvlan1 type macvlan macaddr add 00:44:44:44:44:44

This allows clients with MAC addresses 00:11:11:11:11:11,
00:22:22:22:22:22 to be part of only VLAN associated with macvlan0
interface. Clients with MAC addresses 00:44:44:44:44:44 with only VLAN
associated with macvlan1 interface. And client with MAC address
00:33:33:33:33:33 to be associated with both VLANs.

Based on work of Stefan Gula <steweg@gmail.com>

v8: last version of Stefan Gula for Kernel 3.2.1
v9: rework onto linux-next 2014-03-12 by Michael Braun
    add MACADDR_SET command, enable to configure mac for source mode
    while creating interface
v10:
  - reduce indention level
  - rename source_list to source_entry
  - use aligned 64bit ether address
  - use hash_64 instead of addr[5]
v11:
  - rebase for 3.14 / linux-next 20.04.2014
v12
  - rebase for linux-next 2014-09-25

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
Signed-off-by: David S. Miller <davem@davemloft.net>